The use of the Internet worldwide is ever increasing with a high growth rate in the developing countries around the world. However, many emerging business centers in regions near the Equator are handicapped by poor connectivity to the Internet. These centers are typically located in countries with limited national high bandwidth network infrastructure, and sometimes surrounded by either hostile neighbors or inhospitable terrain that makes terrestrial and undersea cable connections impractical.
Nevertheless, there is a continuing demand for high bandwidth connectivity to the Internet in these countries. Many of the most rapidly growing markets are both near the Equator and poorly connected via undersea cables. For some of the larger countries, the internal network infrastructure is relatively primitive. Furthermore, natural disasters can also disrupt connections, and the ability to rapidly reconfigure a communication network to reconnect the affected areas can be extremely valuable. In addition to the underserved markets, the major global telecom carriers of significant and growing wholesale bandwidth have needs for backup and replacement bandwidth to maintain Quality of Service agreements.
Geostationary Earth Orbit (GEO) communication satellites have inherently high latency, while other satellite communication networks suffer from some combination of limited worldwide connectivity, low bandwidth, or cost. The GEO satellites offer coverage of a reasonably large fraction of the Earth per satellite but have long communication paths (˜36,000 km) resulting in a signal latency of at least 120 msec per path. Moreover, multiple bounces may be required to provide routing, and connection between ground sites not within footprint of same satellite may require ground connections. Additionally, GEO communication satellites are currently restricted to Radio Frequency (RF) signals, which limit available bandwidth to a range of hundreds of MHz to a few GHz. Furthermore, multiple beams need to be used to provide relatively high total throughput per satellite (72 beams at 48 Mbps is typical, for 3.4 Gbps per satellite).
The “Other 3 Billion” (O3B) program is attempting to serve the same general equatorial region using Radio Frequency (RF) signals. As a result of RF usage, O3B has severe bandwidth restrictions. O3B uses a Medium Earth Orbit (MEO) constellation of 8 to 12 satellites in Equatorial orbit at 8,000 km. Each satellite will have up to 10 RF links that will (eventually) be capable of up to 1.2 Gbps per channel. The constellation is rated at 70 total ground sites at 1.2 Gbps per ground site, or 84 Gbps total, and the satellite network is divided into 7 regions, with a single gateway per region. O3B also has no inter-satellite links, so communicating across regional boundaries requires multiple bounces.
The Iridium™ constellation simply doesn't have the bandwidth to address the same market. Iridium's™ Low Earth Orbit (LEO) constellation has an altitude of about 780 km, which limits access per satellite. Accordingly, a constellation of 66 active satellites is used to provide 24/7 coverage of the entire world. Use of L-band in LEO constellation limits the bandwidth of satellite phones to less than 1 Mbps. Gateway links offer 10 Mbps of bandwidth to a few selected locations. Moreover, inter-satellite links are RF, with substantially limited bandwidth.
Some limited experiments were conducted for free-space optical communication (FSO), also sometimes referred to as laser communication, or lasercom for short, by the National Aeronautics and Space Administration (NASA) around 2005, in the NASA Mars Telecommunication Orbiter program. However, these experiments proved to have limited coverage duration, limited connectivity, and usually limited bandwidth of about 5-10 Gbps of upper limit per link. No commercial viability was the conclusion of the program.
Several attempts have been made to establish a space-based laser communication network. One such network was the Transformational Communication Architecture (TCA), which was designed around a backbone of GEO satellites with inter-satellite links, and laser links to other spacecrafts and to airborne platforms and ground sites. The estimated cost of TCA was so high that it could not survive and was cancelled at its onset.
All prior attempts at lasercom in space have used an optical to electrical to optical (O-E-O) approach, with the incoming optical signal converted to an electrical signal and then converted back to an outgoing optical signal. The approach has the advantage that the signal can undergo a full re-amplification, re-shaping and re-timing (3R) regeneration on-board while it is in the electronic domain, but the size, weight, and especially power of the hardware has been a severe challenge. Much of the work has also concentrated on using satellites in GEO, for which the range is as much as 6 times further than the MEO satellites.